The overall objectives of this research are to obtain an understanding of eucaryotic protein biosynthesis in molecular terms and to apply such molecular information to an analysis of the mechanisms that underlie changes in cellular physiology. Specific areas proposed as immediate goals are: 1) The resolution and purification of the soluble factors required for protein chain initiation. These factors are quantitated by their participation in a reaction in which natural mRNA catalyzes the incorporation of aminoacyl tRNA into protein. 2) The delineation of the sequence of reactions describing the function of the different components of the protein synthesizing system. Of particular interest are factors that bind the initiator species of methionyl tRNA, that promote the adjunction of initiator methionyl tRNA to the 40S ribosomal subunit, and that catalyze a reaction in which ribosome bound GDP reacts with ATP to form 5'-diphosphoguanosine diphosphate (ppGpp). 3) Mechanisms that regulate the translational availability of particular mRNA(s). The system proposed for analysis is the germinating wheat embryo which utilizes, in a differential manner, a store of preformed mRNA for its early development.